The present disclosure relates to a data processing device and an image forming apparatus of a tandem type.
In an image forming apparatus of a tandem type, an exposure device forms a plurality of electrostatic latent images for a plurality of colors on a plurality of image carriers that rotate with a predetermined period. The plurality of electrostatic latent images are developed as a plurality of toner images on the plurality of image carriers. The plurality of toner images are overlaid on an intermediate transfer belt. This allows a color image to be formed.
The distance between the image carrier and the exposure device may vary during the period (hereinafter referred to as a “rotation period”) with which the image carrier rotates. In addition, the variation of the distance during the rotation period may differ among the plurality of image carriers. As a result, in the image forming apparatus, the plurality of toner images of the plurality of colors may be overlaid on the intermediate transfer belt in a state of being shifted from each other in a main scanning direction.
In the image forming apparatus, a specific color image for a shift inspection is formed on the intermediate transfer belt before the image formation. The specific color image includes a plurality of specific patterns of the plurality of colors that are aligned in a sub scanning direction. For example, as a related technology, there is known an image forming apparatus that derives shift amounts in the main scanning direction of the plurality of specific patterns of the plurality of colors, based on specific image data that is obtained by optically reading the specific color image.